The distribution and stability of aflatoxin M-1 (AFM(1)) in Kashar cheese were investigated. Raw milk samples were spiked with AFM(1) at the levels of 50, 250 and 750 ng/L. Distribution of toxin in milk, cheese curd, whey, kneading brine and cheese, and its stability during ripening were determined by high-performance liquid chromatography. Concentrations of AFM(1) in curds for each contamination level were 2.93, 3.19 and 3.37 times higher than those in milk. After syneresis, the percentage distribution of AFM(1) was 40-46% in curds and 53-58% in whey indicating that relatively higher concentration of toxin passed to whey. Moreover, by the kneading process approximately 2-5% of AFM(1) passed to kneading brine. Compared to the initial spiking level, the percentage of toxin in cheeses varied between 35-42%. Over a 60-day storage period, there was no decrease in the concentration of AFM(1), suggesting that the toxin was stable during ripening.